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          <h1 class="post-title" itemprop="name headline">Java集合-集合框架概述</h1>
        

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<p>【转载】<a href="http://yikun.github.io/2015/03/31/Java%E9%9B%86%E5%90%88%E6%A1%86%E6%9E%B6/" target="_blank" rel="noopener">原文链接</a></p>
</blockquote>
<h3 id="1-概述"><a href="#1-概述" class="headerlink" title="1. 概述"></a>1. 概述</h3><h4 id="什么是集合？"><a href="#什么是集合？" class="headerlink" title="什么是集合？"></a>什么是集合？</h4><p>这Java官方的<a href="https://docs.oracle.com/javase/tutorial/collections/intro/index.html" target="_blank" rel="noopener">入门文档</a>是这样描述集合的：</p>
<blockquote>
<p>Collection(有时候也叫container)是一个简单的对象，它把多个元素组织成一个单元。集合可以用来存储、检索、操作、通信。通常情况下，集合代表了一个自然数据项，比如一组手牌(牌的集合)、邮件文件夹(邮件的集合)、电话目录(姓名到电话的映射)。如果你使用过Java或者其他语言，你应该很熟悉集合。</p>
</blockquote>
<a id="more"></a>



<h4 id="什么是集合框架？"><a href="#什么是集合框架？" class="headerlink" title="什么是集合框架？"></a>什么是集合框架？</h4><blockquote>
<p>Collections Framework是一个用来表示和操作集合的统一的架构。集合的框架包括了：</p>
<ul>
<li><strong>Interfaces:</strong><br>这些是表示集合的抽象数据类型，接口允许集合完成操作，独立与其详细的实现。在面向对象的语言中，接口构成了体系架构；</li>
<li><strong>Implementations:</strong><br>这些是接口的具体实现。本质上，是一些可复用的数据结构；</li>
<li><strong>Algorithms:</strong><br>这些方法可以对接口实现的对象进行有用的计算，比如搜索、排序。这些算法是具有多态性的：也就是说，同样的方法可以用在合适的接口的不同实现。本质上，是一些可复用的函数。</li>
</ul>
<p>除了Java的集合框架，还有一些著名的集合框架的例子：比如C++的STL和Smalltalk的集合架构。从历史上来看，集合框架可能比较复杂，也可能有一些很陡峭的学习曲线。不过我们相信Java的集合框架会突破这样的传统，在这章你就可以自己学会。</p>
</blockquote>
<h4 id="使用集合框架有什么好处？"><a href="#使用集合框架有什么好处？" class="headerlink" title="使用集合框架有什么好处？"></a>使用集合框架有什么好处？</h4><blockquote>
<p>Java的集合框架提供了一下优点：</p>
<ul>
<li><strong>减少编程的工作量</strong>：通过提供有用的数据结构和算法，集合框架能让你更专注的实现程序的核心功能，而不是去做一个底层的“管道工”。Java框架通过促进无关API的互操作性，使得你不用自己去实现不同API的适配</li>
<li><strong>提高程序的速度与质量</strong>：集合框架提供了一些有用数据结构和算法的高性能、高质量的实现。每个接口的不同的实现也是可以互换的，所以程序可以通过切换集合来做一些调整。正因为你从实现数据结构的那些苦差事中脱离出来，你才可以有更多的实现去改善你自己程序的性能和质量</li>
<li><strong>允许无关APIs的互操作</strong>：集合接口是API之间传递集合的一个“方言”，比如我的网络管理API有一个节点名的集合，而GUI工具需要一个列标题的集合，即使是分开实现它们，我们的APIs也可以无缝的接合。</li>
<li><strong>省力地学习和使用新API</strong>：<br>这是另一个领先的优势，设计者和实现者没必要在每次都重新设计API的时候都“推倒重来”地实现集合，而是直接使用标准的集合接口就好了。</li>
<li><strong>促进软件的复用</strong>：符合标准集合接口的新数据结构本质上是可以复用的。对于操作这些新数据结构算法也是一样可以复用的。</li>
</ul>
</blockquote>
<p>因此，后面也便从接口、实现、算法几方面结合着代码和官方的文档学习总结一下。</p>
<h3 id="2-接口"><a href="#2-接口" class="headerlink" title="2. 接口"></a>2. 接口</h3><p><img src="http://cdn.briarbear.cn/201806251525_9.png" alt></p>
<p>在Java中所有的核心集合接口都是generic的</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Collection</span>&lt;<span class="title">E</span>&gt; <span class="keyword">extends</span> <span class="title">Iterable</span>&lt;<span class="title">E</span>&gt; </span>&#123;&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">List</span>&lt;<span class="title">E</span>&gt; <span class="keyword">extends</span> <span class="title">Collection</span>&lt;<span class="title">E</span>&gt; </span>&#123;&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Queue</span>&lt;<span class="title">E</span>&gt; <span class="keyword">extends</span> <span class="title">Collection</span>&lt;<span class="title">E</span>&gt; </span>&#123;&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Deque</span>&lt;<span class="title">E</span>&gt; <span class="keyword">extends</span> <span class="title">Queue</span>&lt;<span class="title">E</span>&gt; </span>&#123;&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Set</span>&lt;<span class="title">E</span>&gt; <span class="keyword">extends</span> <span class="title">Collection</span>&lt;<span class="title">E</span>&gt; </span>&#123;&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">SortedSet</span>&lt;<span class="title">E</span>&gt; <span class="keyword">extends</span> <span class="title">Set</span>&lt;<span class="title">E</span>&gt; </span>&#123;&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">NavigableSet</span>&lt;<span class="title">E</span>&gt; <span class="keyword">extends</span> <span class="title">SortedSet</span>&lt;<span class="title">E</span>&gt; </span>&#123;&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">Map</span>&lt;<span class="title">K</span>,<span class="title">V</span>&gt; </span>&#123;&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">SortedMap</span>&lt;<span class="title">K</span>,<span class="title">V</span>&gt; <span class="keyword">extends</span> <span class="title">Map</span>&lt;<span class="title">K</span>,<span class="title">V</span>&gt; </span>&#123;&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">interface</span> <span class="title">NavigableMap</span>&lt;<span class="title">K</span>,<span class="title">V</span>&gt; <span class="keyword">extends</span> <span class="title">SortedMap</span>&lt;<span class="title">K</span>,<span class="title">V</span>&gt; </span>&#123;&#125;</span><br></pre></td></tr></table></figure>

<p>也就是说在声明一个Collection的时候，应该指定一种类型。官方是这样解释原因的：</p>
<blockquote>
<p>Specifying the type allows the compiler to verify (at compile-time) that the type of object you put into the collection is correct, thus reducing errors at runtime.</p>
</blockquote>
<p>下面就来介绍一下几种接口：</p>
<ul>
<li><strong>Collection</strong>： 集合层次中的根。一个集合表示一组对象。有些有序，有些无序。有些重复，有些重复。Collection没有直接的实现，而只有它的子接口的对应的实现。</li>
<li><strong>Set</strong>：<strong>不能包含重复的元素</strong>，比如扑克手牌、学生选课计划、计算机的进程。</li>
<li><strong>List</strong>：有序的集合，也可以包含重复的元素。用于对每个元素精确的控制，比如插入、用index来索引。</li>
<li><strong>Queue</strong>：用于多元素有优先级的处理，可以用做FIFO</li>
<li><strong>Deque</strong>：用于多元素有优先级的处理，double ended queue，可以用作FIFO，LIFO</li>
<li><strong>Map</strong>：用于keys到values的映射，不能包含重复元素<br>另外还提供了2个带排序的Set和Map。</li>
<li><strong>SortedSet</strong>：<strong>元素升序</strong></li>
<li><strong>SortedMap</strong>：<strong>key升序</strong></li>
</ul>
<p>在1.6版本开始，还有两种新的接口<strong>NavigableSet</strong>、<strong>NavigableMap</strong>。</p>
<blockquote>
<p>A SortedMap/SortedSet extended with navigation methods reporting closest matches for given search targets.</p>
</blockquote>
<p>提供诸如：</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">//返回第一个大于e的元素</span></span><br><span class="line"><span class="function">E <span class="title">higher</span><span class="params">(E e)</span></span>;</span><br></pre></td></tr></table></figure>

<p>之类的“导航性质”的便捷操作。</p>
<p>以上便是Java集合框架与接口的相关内容。</p>
<hr>
<h3 id="3-类图"><a href="#3-类图" class="headerlink" title="3. 类图"></a>3. 类图</h3><ul>
<li>常见Map类相关的实现与继承关系</li>
</ul>
<p><img src="http://cdn.briarbear.cn/201806261549_597.png" alt></p>
<ul>
<li>常见List Set类相关实现与继承关系</li>
</ul>
<p><img src="http://cdn.briarbear.cn/201806261624_532.png" alt></p>

      
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